Biomechanics of Lumbar spine

Question 1

Function of lumbar spine

Answer 1

Support / WB,
Trunk mobility and locomotions
Protect spinal cord and cauda equina

Question 2

key features of lumbar vertebrae

Answer 2

kidney shaped vertebral body
triangle shaped vertebral canal
broad plates for ligament attach
articular processes at junction laminae and pedicles

Question 3

function spinous and transverse process of lumbar vertebrae

Answer 3

provides levers for muscle and ligaments to cause or restrict movement
stabilise vertebral column

Question 4

function of apophyseal joint

Answer 4

Apophyseal joint - guides intervertebral motion

Question 5

function of interbody joint

Answer 5

absorbs shock,
distributes load,
intervertebral stability,
approximate site of axes rotation for movement

Question 6

constituents of IV disc

Answer 6

water
proteoglycan
collagen - Type I and Type II
Nucleus Pulposus
Annulus fibrosis
vertebral end plate

Question 7

Composition of nucleus pulposus

Answer 7

70-90% water
65% proteoglycans
15-20% collagen
jelly like material
allow vertebrae to withstand compression and force

Question 8

composition of annulus fibrosis

Answer 8

60-70% water
50-60% collagen
15%proteoglycan acts as binding in laminae

Question 9

function vertebral end plate

Answer 9

covers NP but not all of AF.
Strongly attached to AF more than VB so can be ripped from VB in trauma.
Provides nutrition to disc.

Question 10

describe load transmission in IV disc

Answer 10

force from nucleus radially deviates circumferentially under axial pressure annular fibres
when annular fibres reach their elastic limit inward force is exerted back on nucleus pulposus
nucleus pulposus exerts downward pressure
weight is transmitted to vertebral below

Question 11

function dorsal rami

Answer 11

supply posterior spinal structures

Question 12

capsule and nerve supply in facet joint

Answer 12

ligamentum flavum anterior
dorsal ramus

Question 13

example of rotation

Answer 13

osteokinematic
force couple
torque

Question 14

example of translation

Answer 14

arthrokinematic
shear force e.g. cephalad, caudad

Question 15

stress definition

Answer 15

elongating force

Question 16

strain definition

Answer 16

extent to which a fibre is elongated e.g. tension, compression, shear and torsion

Question 17

stiffness

Answer 17

resistance to deformation
greater stiffness = greater bonding between collagen fibres /matrix

Question 18

explain biomechanics of lumbar flexion

Answer 18

Increase IV disc pressure and nucleus pulposus posteriorly,
Facet joints slide open and no longer a gap
Posterior ligament stretched
EOR restraints - rotation - posterior facet joint capsule ligaments and muscle stretch, translation - facet joints - stabilise segment and protect against shear

Question 19

biomechanics of lumbar extension

Answer 19

reduced IV disc pressure posteriorly compression relative to anterior stretch
Nucleus pulposus anteriorly
facet joints slide closed
anterior ligaments stretched
bony block - inferior articular processes impact lower face of superior articular processes of vertebra below

Question 20

explain biomechanics of lumbar rotation

Answer 20

AR rings limit torsion strain
collagen fibres AF if strain 4% length sustain damage
IVD resist rotation more than flexion